A sonobuoy is a buoy equipped with an acoustic receiver and a radio transmitter that emits radio signals when it detects underwater sounds. Sonobuoys have been deployed into the ocean to aid in the detection of submarines and other vessels. Some sonobuoys are equipped with devices that emit signals and receive the resulting echo. Others are capable of detecting noise generated by crafts, such as submarines. By deploying a number of sonobuoys, the location of such crafts can be determined.
Deployment of sonobuoys is generally accomplished by launching the buoys from aircraft. Sonobuoys are often deployed in remote locations and far enough away from each other such that it is inconvenient, difficult, or impossible to provide power to them on an ongoing basis and/or in a stored form. As such, the lifetime of a buoy is typically at least partially dependent on how much electrical energy it has stored on board. On-board sources of electrical energy may comprise, for example, a seawater activated battery or other electro-chemical energy source. Unfortunately, the amount of electrical energy that is stored on-board is often insufficient to power a buoy for what would otherwise be its useful life. Shortened lifespan due to an inadequate supply of onboard power applies to other apparatus as well such as floating navigational beacons.
A possible solution to the problem of inadequate on-board electrical energy storage is to have the apparatus generate electrical energy from wave motion. Many approaches have been developed in the past to harness this natural energy source. One approach is to utilize the energy potential derived from a swinging or rotating pendulum, but unless kept very small relative to the sonobuoy, such a device would have the tendency to tip the sonobuoy on its side rendering it useless. The power generating capability of such a system is also often inadequate during heavy wave action. Another approach is the use of piezoelectric polymer systems that generate electricity as the wave action on the buoy stretches a polymer anchor hose, but such an approach is often unsatisfactory for a variety of reasons. Moreover, large turbines, pipes, and complex mechanical structures are not practical for a small buoy generator either.